Field of the Invention
The present invention relates to an image forming apparatus that forms an image by using the electrophotographic process, such as a copying machine, a printer, a facsimile machine, or a multifunction printer.
Description of the Related Art
Hitherto, for example, as an electrophotographic image forming apparatus, there is an image forming apparatus in which toner images primarily transferred from photosensitive members of a plurality of image forming units to an intermediate transfer belt are secondarily transferred to a recording medium to output an image. The image forming units each have a photosensitive member, a charging member, a developing member and the like, and are arranged in a row along the moving direction of the intermediate transfer belt.
In such an image forming apparatus, the temperature in the apparatus rises as the operation continues. The causes include accumulation of heat of a fixing unit that fixes a toner image to a recording medium in the main body of the apparatus, heat generation of electric parts such as a motor and a power supply, and frictional heat in a rubbing part of an operating part such as a roller. The temperature rise in the main body of the apparatus causes an image defect. In some cases, toner may adhere to each member. Therefore, it is necessary to provide a fan as a cooling unit in the image forming apparatus, and to suppress the temperature rise in the main body of the apparatus with the fan.
Japanese Patent Laid-Open No. 2003-241591 discloses an opening region that is provided in each image forming unit in order to irradiate a photosensitive member with irradiation light forming an electrostatic latent image. Japanese Patent Laid-Open No. 2003-241591 proposes using this opening region as an air duct to each image forming unit and causing air to flow to each image forming unit through this air duct. Owing to this configuration, the opening region can be used as an air duct, and therefore, the size of the main body of the apparatus can be reduced.
However, in the configuration of Japanese Patent Laid-Open No. 2003-241591, an air supply portion of a duct that guides air supplied from a fan, and an opening portion that is connected to the air supply portion and that guides air into each image forming unit, have a shape such that they widely open in the axial direction of the photosensitive member, and therefore, it is difficult to efficiently cool the photosensitive member, a developing roller, and others.
Image forming apparatuses are desired to be further speeded up. In that case, the peripheral speed of rotating members such as a photosensitive member and a developing roller increases, and therefore, self heat generation in each member also increases. In the case where the opening portion and the air supply portion each have a shape such that they widely open in the axial direction of the photosensitive member, when each member locally significantly generates heat, it is difficult to intensively cool those parts. In the case where the opening portion and the air supply portion have a shape such that they widely open in the axial direction of the photosensitive member, air from the cooling unit is supplied to the entire region in the axial direction of the photosensitive member, and therefore toner may be scattered from each member.